Model predictive battery power limit estimation systems and methods

ABSTRACT

Systems and methods for improving operation of an automotive battery system including an automotive electrical system comprising a battery system that uses operational parameters, predicted internal resistance of a battery expected over a prediction horizon, and real-time internal resistance of a battery to increase performance and reliability. The battery system includes a battery electrically coupled to electrical devices in the automotive system, sensors coupled to the battery that determine terminal voltage of battery, and a battery control system communicatively coupled to sensors. The battery control system determines a charging power limit used to control supply of electrical power to the battery when charging the battery, based on predicted internal resistance when measured terminal voltage of the battery is not greater than a lower voltage threshold and based on a real-time internal resistance of the battery when the measured terminal voltage of the battery is greater than the lower voltage threshold.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. §371 of International Application No. PCT/US17/59380, entitled “MODELPREDICTIVE BATTERY POWER LIMIT ESTIMATION SYSTEMS AND METHODS,” filedOct. 31, 2017, which claims priority to and the benefit of U.S.Provisional Application No. 62/415,280, entitled “INTEGRATING FEEDBACKCONTROL ALGORITHMS WITH A LITHIUM-ION BATTERY MODEL FOR REAL TIME POWERLIMIT ESTIMATION,” filed Oct. 31, 2016, which are each incorporatedherein by reference in their entireties for all purposes.

BACKGROUND

The present disclosure generally relates to battery systems and, morespecifically, to battery control systems utilized in battery systems.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present techniques,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

Electrical systems often include a battery system to capture (e.g.,store) generated electrical energy and/or to supply electrical power. Infact, battery systems may be included in electrical systems utilized forvarious applications. For example, a stationary power system may includea battery system that receives electrical power output by an electricalgenerator and stores the electrical power as electrical energy. In thismanner, the battery system may supply electrical power to electricalloads using the stored electrical energy.

Additionally, an electrical system in an automotive vehicle may includea battery system that supplies electrical power, for example, to provideand/or supplement the motive force (e.g., power) of the automotivevehicle. For the purpose of the present disclosure, such automotivevehicles are referred to as xEV and may include any one, any variation,and/or any combination of the following type of automotive vehicles. Forexample, electric vehicles (EVs) may utilize a battery-powered electricpropulsion system (e.g., one or more electric motors) as the primarysource of vehicular motive force. As such, a battery system in anelectric vehicle may be implemented to supply electrical power to thebattery-powered electric propulsion system. Additionally, hybridelectric vehicles (HEVs) may utilize a combination of a battery-poweredelectric propulsion system and an internal combustion engine propulsionsystem to produce vehicular motive force. As such, a battery system maybe implemented to facilitate directly providing at least a portion ofthe vehicular motive force by supplying electrical power to thebattery-powered electric propulsion system.

Micro-hybrid electric vehicles (mHEVs) may use an internal combustionengine propulsion system as the primary source of vehicular motiveforce, but may utilize the battery system to implement “Stop-Start”techniques. In particular, a mHEV may disable its internal combustionengine while idling and crank (e.g., restart) the internal combustionengine when propulsion is subsequently desired. To facilitateimplementing such techniques, the battery system may continue supplyingelectrical power while the internal combustion engine is disabled andsupply electrical power to crank the internal combustion engine. In thismanner, the battery system may indirectly supplement providing thevehicular motive force.

To facilitate controlling its operation, a battery system often includesa battery control system, for example, that determines a battery state,such as state-of-function (SoF), state-of-health (SoH), and/orstate-of-charge (SoC). In some instances, charging and/or discharging ofa battery (e.g., battery module, battery pack, or battery cell) may becontrolled based at least in part on a corresponding battery statedetermined by the battery control system. For example, magnitude ofcurrent and/or voltage supplied to charge the battery may be controlledbased at least in part on a charging power limit indicated by itscorresponding state-of-function. Thus, at least in some instances,accuracy of a battery state determination by a battery control systemmay affect operational stability and/or operational efficiency of itscorresponding battery system.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

In one embodiment, an automotive electrical system includes a batterysystem that includes a battery configured to be electrically coupled toone or more electrical devices in the automotive electrical system, oneor more sensors electrically coupled to the terminals of the battery,and a battery control system communicatively coupled to the one or moresensors measuring terminal voltage of the battery. The battery controlsystem is programmed to determine a predicted internal resistance of thebattery, where the predicted internal resistance based on projectedoperational conditions (state-of-charge, temperature, power usage,etc.). The battery control system also determines a charging power limitused to control supply of electrical power to the battery based on thepredicted internal resistance when the measured terminal voltage of thebattery is not greater than a lower voltage threshold. When the measuredterminal voltage of the battery is greater than the lower voltagethreshold, the battery control system determines a real-time internalresistance of the battery based on the measured terminal voltage of thebattery and a battery model that describes a relationship betweenmeasured battery parameters and internal resistance of the battery, anddetermines the charging power limit based on the real-time internalresistance to facilitate improving operational reliability of thebattery.

In a second embodiment, a method for controlling charging of a batterycell in an automotive vehicle includes determining, using a controlsystem, measured terminal voltage of the battery cell based on sensordata, a predicted internal resistance of the battery cell, and acharging power limit. The predicted internal resistance based onprojected operational conditions (state-of-charge, temperature, powerusage, etc.). When the measured terminal voltage of the battery cell isnot greater than a lower voltage threshold, the charging power limit isbased on the predicted internal resistance of the battery cell. When themeasured terminal voltage of the battery cell is greater than the lowervoltage threshold, the charging power limit is based on a real-timeinternal resistance of the battery cell, where the real-time internalresistance of the battery cell is determined based on a battery modelthat relates measured operational parameters to model parameterscomprising internal resistance. The control system instructs anelectrical power source to adjust charging power supplied to the batterycell based on the charging power limit when a target charging power isgreater than the charging power limit.

In a third embodiment, a tangible, non-transitory, computer-readablemedium stores instructions executable by one or more processors of anautomotive control system. The instructions include determining, usingthe one or more processors, measured terminal voltage of an automotivebattery module based on sensor data, a predicted internal resistance ofthe automotive battery module expected to occur over a predictionhorizon, a charging current limit, and instruct the automotive batteryto supply electrical power to an electrical device in an automotivevehicle based on the discharging current limit. The discharging chargingcurrent limit is based on the predicted internal resistance of theautomotive battery module when the measured terminal voltage of theautomotive battery module is not greater than a lower voltage threshold.When the measured terminal voltage of the automotive battery module isgreater than the lower voltage threshold, the discharging limit is basedon a real-time internal resistance of the automotive battery module. Thereal-time internal resistance of the automotive battery module isdetermined by a battery model that relates measured battery parametersto model parameters comprising internal resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure may be better understood uponreading the following detailed description and upon reference to thedrawings, in which:

FIG. 1 is a perspective view of an automotive vehicle including abattery system, in accordance with an embodiment;

FIG. 2 is a block diagram of the battery system of FIG. 1, in accordancewith an embodiment;

FIG. 3 is a circuit diagram of a battery model used by the batterysystem of FIG. 1, in accordance with an embodiment;

FIG. 4 is a flow diagram of a process for operating the battery systemof FIG. 1, in accordance with an embodiment;

FIG. 5 is a flow diagram of a process for determining operationalparameters of a battery in the battery system of FIG. 1, in accordancewith an embodiment;

FIG. 6 is a flow diagram of a process for determining state of thebattery in the battery system of FIG. 1, in accordance with anembodiment; and

FIG. 7 is a flow diagram of a process for controlling charging of thebattery in the battery system of FIG. 1, in accordance with anembodiment.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. These described embodiments are only examples of thepresently disclosed techniques. Additionally, in an effort to provide aconcise description of these embodiments, all features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but may nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

Generally, a battery system may be implemented to capture (e.g., store)electrical energy generated by one or more electrical generators and/orto supply electrical power to one or more electrical loads using storedelectrical energy. Leveraging these benefits, one or more batterysystems are often included in an electrical system. In fact, batterysystems may be utilized in electrical systems implemented for awide-variety of target applications, for example, ranging fromstationary power systems to vehicular (e.g., automotive) electricalsystems.

In any case, to facilitate controlling its operation (e.g., chargingand/or discharging), a battery system often includes a battery controlsystem. In some instances, charging and/or discharging of a battery(e.g., battery module, battery pack, or battery cell) in the batterysystem may be controlled based at least in part on corresponding batterystates, for example, by a higher-level (e.g., vehicle) control system incoordination with the battery control system. Thus, to facilitatecontrolling operation of the battery system, its battery control systemmay determine battery states by executing control applications based atleast in part on operational parameters (e.g., voltage, current, and/ortemperature) of the battery.

For example, based at least in part on current flow through the battery,the battery control system may execute a state-of-charge (SoC)application to determine (e.g., predict or estimate) open-circuitvoltage (OCV) of the battery. Additionally or alternatively, based atleast in part on current and/or voltage of a battery, the batterycontrol system may execute a state-of-health (SoH) application todetermine internal resistance of the battery. Additionally oralternatively, based at least in part on temperature and/or internalresistance of a battery, the battery control system may execute astate-of-function (SoF) application to determine a power (e.g., voltageand/or current) limit for charging and/or discharging the battery.

Based at least in part on battery state, in some instances, a batterycontrol system may directly control operation of a corresponding batterysystem by outputting control commands (e.g., signals) that instruct thebattery system to perform one or more control actions. For example, thebattery control system may output a control command that instructs aswitching device electrically coupled between a battery in the batterysystem and an electrical generator (e.g., alternator) to switch from aclosed (e.g., electrically connected) position to an open (e.g.,electrically disconnected) position when state-of-charge of the batteryexceeds a state-of-charge threshold. Additionally or alternatively, abattery control system may facilitate controlling operation of acorresponding battery system by communicating battery state data to ahigher-level control system, which is implemented to control operationof one or more devices (e.g., equipment or machines) external from thebattery system. For example, based at least in part on data indicativeof battery state-of-function, a vehicle control unit may output acontrol command that instructs an alternator to adjust current and/orvoltage of electrical power output to the battery system.

To facilitate improving operation of a battery system, in someinstances, its battery control system may predict (e.g., estimate)battery states based at least in part on operational parametersdetermined via a battery (e.g., pack or cell) model, for example, tofacilitate selecting between candidate control strategies (e.g.,actions). In other words, the battery control system may determinemodeled (e.g., predicted) operational parameters of the battery systembased at least in part on the battery model. Additionally oralternatively, the battery control system may determine measured (e.g.,real-time) operational parameters of the battery system based at leastin part on sensor data received from one or more sensors.

Thus, at least in some instances, operation of a battery system may becontrolled in different manners in response to different battery statesand/or different operational parameters. As such, when operation of abattery system is controlled based on a predicted battery statedetermined by its battery control system, accuracy of the predictedbattery state relative to a corresponding real-time battery state and/oraccuracy of a modeled operational parameter relative to a measuredoperational parameter may affect operational reliability and/oroperational efficiency of the battery system. For example, when greaterthan an actual charge power limit, supplying electrical power to abattery in accordance with a determined charge power limit may decreasesubsequent lifespan and, thus, reliability of the battery. Additionallyor alternatively, when less than an actual state-of-charge,disconnecting electrical power used to charge a battery based on adetermined state-of-charge may decrease amount of captured electricalenergy and, thus, operational efficiency of the battery system.

In some instances, modeled operational parameters of a battery systemmay differ from measured operational parameters, for example, due toinaccuracies in the battery model. Thus, a predicted (e.g., modeled)battery state determined based on the modeled operational parameters mayalso differ from a real-time (e.g., measured) battery state determinedbased on the measured operational parameters. Moreover, in someinstances, the modeled battery state and the measured battery state maydiffer due to inaccuracies in a corresponding control application. Atleast in some instances, controlling operation when such discrepanciesoccur may affect operational reliability and/or operational efficiencyof a battery system, for example, by resulting in a battery module beingelectrically disconnected before being charged up to the state-of-chargethreshold, thereby limiting energy storage provided by the batterysystem and/or ability of the battery system to subsequently crank aninternal combustion engine.

Accordingly, the present disclosure provides techniques to facilitateimproving operation of a battery system, for example, by improvingaccuracy of online (e.g., real-time or near real-time) battery statedetermination. To facilitate online battery state determination, abattery control system may receive sensor data indicative of operationalparameters of a battery (e.g., battery module or battery cell)implemented in the battery system. For example, during operation of thebattery system, the battery control system may receive sensor dataindicative of temperature of a battery module, current flow through thebattery module, terminal voltage of the battery module, and/or voltageacross one or more battery cells in the battery module.

In some embodiments, lifespan of a battery may be improved bymaintaining terminal voltage of the battery below an upper (e.g.,maximum) voltage threshold. To reduce likelihood of sensor (e.g.,measurement) error resulting in terminal voltage exceeding the uppervoltage threshold, in some embodiments, a battery control system maybegin de-rating the battery system before terminal voltage of thebattery reaches the upper voltage threshold. For example, the batterycontrol system may limit current and, thus, charging power supplied tothe battery based at least in part on relationship (e.g., difference)between the terminal voltage and a lower voltage threshold.

In some embodiments, a battery control system may determine a powerlimit for charging and/or discharging a battery based at least in parton internal resistance of the battery. Generally, internal resistance ofa battery is dynamic during operation and over the course of its lifespan. For example, the internal resistance a lithium-ion battery mayincrease as the battery ages. Additionally, the internal resistance of alithium-ion battery may be inversely related to its temperature.Furthermore, the internal resistance of a lithium-ion battery may pulse(e.g., spike) during operation, for example, when the lithium ionbattery is charged during regenerative braking or discharged during astart-stop operation.

To facilitate accounting for the dynamic nature, in some embodiments, abattery control system may predict internal resistance of a battery overa prediction horizon (e.g., period of time) based on projectedoperational conditions (state-of-charge, temperature, power usage,etc.). Generally, controlling charging and/or discharging of a batteryin accordance with a power limit determined based at least in part onits predicted internal resistance may be sufficient to maintain voltageof the battery below the upper voltage threshold. However, in someinstances (e.g., corner cases), controlling operation of the battery inthis manner may affect operational efficiency of the battery system, forexample, due to difference between the predicted internal resistance andactual internal resistance of the battery resulting in battery voltagerapidly oscillating if control algorithm is not properly designed. Infact, when implemented in an automotive vehicle, such battery voltageoscillations may affect drivability, for example, by causing lurches inmovement of the automotive vehicle.

To facilitate reducing likelihood of producing rapid battery voltageoscillations, in some embodiments, a battery control system maydetermine a real-time (e.g., instantaneous) internal resistance based atleast in part on presently determined (e.g., measured) operationalparameters. For example, using a battery model, the battery controlsystem may determine the real-time internal resistance of a batterybased at least in part on presently determined current and terminalvoltage of the battery. Since determined based on presently determinedoperational parameters, at least in some instances, the real-timeinternal resistance may more accurately represent the actual internalbattery resistance at a specific point in time, for example, compared toa predicted internal resistance that is averaged over a longer period oftime.

Nevertheless, to facilitate improving processing latency, a batterycontrol system may generally determine power limits based on predictedinternal resistance, but determine the power limits based on real-timeinternal resistance when charging and/or discharging based on thepredicted internal resistance is expected to result in rapid batteryvoltage oscillations. In some embodiments, a battery control system maydetermine likelihood of producing rapid battery voltage oscillationsbased at least in part on terminal voltage of the battery. For example,when terminal voltage is greater than the lower voltage threshold, thebattery control system may determine that controlling charging using acharging power limit determined based on the predicted internalresistance is expected to result in rapid battery voltage oscillationsand thus, determine the charging power limit based on the real-timeinternal resistance.

By determining charging and/or discharging power limits in this manner,a battery control system may improve accuracy of its state-of-functiondetermination. In a similar manner, the battery control system mayadditionally or alternatively improve accuracy of other battery statedeterminations. As described above, at least in some instances,improving accuracy of battery states determined by a battery controlsystem and used to control operation of a corresponding battery systemfacilitate improving operational reliability and/or operationalefficiency of a battery system and, thus, an electrical system in whichthe battery system is implemented.

To help illustrate, an automotive vehicle 10 with an electrical system,which includes a battery system 12, is shown in FIG. 1. Discussion withregard to the automotive vehicle 10 is merely intended to helpillustrate the techniques of the present disclosure and not to limitscope of the techniques. The automotive vehicle 10 may include thebattery system 12 and an automotive electrical system that controls avehicle console, an electric motor, and/or a generator. In some cases,the battery system 12 may include some or all of the automotiveelectrical system. For sake of discussion, the battery system 12 iselectrically coupled to components in the automotive electrical systemdiscussed. In some embodiments, the automotive vehicle 10 may be an xEV,which utilizes the battery system 12 to provide and/or supplementvehicular motive force, for example, used to accelerate and/ordecelerate the automotive vehicle 10. In other embodiments, theautomotive vehicle 10 may be a automotive vehicle 10 that producesvehicular motive force, for example, using an internal combustion engineto accelerate and/or frictional breaks to decelerate.

A more detailed view of an example automotive electrical systemincluding the battery system 12 is shown in FIG. 2. In the depictedexample, the battery system 12 includes a battery control system 14 andone or more battery modules 16. Additionally, the automotive electricalsystem may include a vehicle console 18 and a heating, ventilating, andair conditioning (HVAC) system 20. In some embodiments, the automotiveelectrical system may additionally or alternatively include a mechanicalenergy source 22 (e.g., an electric motor) operating in a motor mode.

Additionally, in the depicted automotive vehicle 10, the automotiveelectrical system may include an electrical source. In the illustratedexample, the electrical source in the automotive electrical system is analternator 24. The alternator 24 may convert mechanical energy generatedby the mechanical energy source 22 (e.g., an internal combustion engineand/or rotating wheels) into electrical energy. In some embodiments, theelectrical source may additionally or alternatively include themechanical energy source 22 (e.g., an electric motor) operating in agenerator mode.

As depicted, the automotive vehicle 10 includes a vehicle control system26. In some embodiments, the vehicle control system 26 may generallycontrol operation of the automotive vehicle 10 including the electricalsystem. Thus, in the depicted automotive vehicle 10, the vehicle controlsystem 26 may supervise the battery control system 14, the batterymodule 16, the HVAC 20, the alternator 24, the vehicle console 18,and/or the mechanical energy source 22, making the vehicle controlsystem 26 similar to a supervisory control system. However, the vehiclecontrol system 26 may additionally control operation of other componentsother than the components of the electrical system, such as an internalcombustion engine propulsion system.

In some embodiments, the battery control system 14 may additionally oralternatively control operation of the battery system 12. For example,the battery control system 14 may determine operational parameters ofbattery modules 16, coordinate operation of multiple battery modules 16,communicate control commands (e.g., signal) instructing the batterysystem 12 to perform control actions, and/or communicate with thevehicle control system 26.

To facilitate controlling operation of the battery system 12, thebattery control system 14 may include a processor 28 and memory 30. Insome embodiments, the memory 30 may include a tangible, non-transitory,computer readable medium that stores data, such as instructionsexecutable by the processor 28, results (e.g., battery states)determined by the processor 28, and/or information (e.g., operationalparameters) to be analyzed/processed by the processor 28. Thus, in suchembodiments, the memory 30 may include random access memory (RAM), readonly memory (ROM), rewritable non-volatile memory (e.g., flash memory),hard drives, optical discs, and the like. Additionally, the processor 28may include one or more general purpose processing units, processingcircuitry, and/or logic circuitry. For example, the processor 28 mayinclude one or more microprocessors, one or more application-specificintegrated circuits (ASICs), and/or one or more field programmable logicarrays (FPGAs).

Additionally, to facilitate the storing and supplying of electricalpower, the battery system 12 may include one or more battery modules 16.In some embodiments, storage capacity of the battery system 12 may bebased at least in part on number of battery modules 16. Additionally, insome embodiments, operational compatibility of the battery system 12with the automotive electrical system may be based at least in part onconfiguration of the battery modules 16, for example, in series and/orin parallel to operate in a target voltage domain. According, in someembodiments, implementation (e.g., number and/or configuration) of thebattery modules 16 and, thus, the battery system 12 may vary based atleast in part on configuration and/or target application of theautomotive electrical system.

As described above, the number and/or configuration of battery modules16 of the battery system 12 may vary based at least in part on targetapplication. For example, in the depicted automotive vehicle 10, thebattery system 12 includes the battery module 16. In some embodiments,the battery module 16 may include one or more battery cells 32 connectedin series and/or parallel with terminals of the battery module 16.

Additionally, in some embodiments, the battery system 12 may includemultiple battery modules 16 to facilitate improving applicationflexibility and/or application ease. For example, the battery system 12may include a first battery module 16 and a second battery module 16,which each includes one or more battery cells 32, connected in seriesand/or in parallel. It is noted that the battery system 12 may includemultiple battery modules 16 to facilitate operational compatibility withmultiple voltage domains. For example, the first battery module 16 mayoperate (e.g., receive and/or supply) using electrical power in a first(e.g., high or 48 volt) voltage domain while the second battery module16 operates using electrical power in a second (e.g., low or 12 volt)voltage domain.

In any case, the battery control system 14 may be communicativelycoupled to one or more sensors 34 to facilitate monitoring operation ofa battery module 16 or the battery system 12 as a whole. In particular,a sensor 34 may transmit sensor data to the battery control system 14indicative of real-time (e.g., measured) operational parameters of thebattery modules 16. Thus, in some embodiments, the battery controlsystem 14 may be communicatively coupled to one or more voltage sensors34, one or more temperature sensors 34, and/or a variety of additionalor alternative sensors 34. For example, in the depicted embodiment, thebattery control system 14 may receive sensor data from the sensor 34indicative of the voltage (e.g., terminal voltage) of the battery module16 and/or current flow through the battery module 16.

In some embodiments, the battery control system 14 may process thesensor data based on instructions stored in memory 30. For example, thebattery control system 14 may store a battery model 42 and a controlapplication 44 as instructions in memory 30. As discussed above, thebattery control system 14 may execute the control application 44 todetermine the state of a battery (e.g., battery module 16 and/or batterycell 32) in the battery system 12. For example, the battery controlsystem 14 may execute a state-of-function control application 44 todetermine a discharge current limit and/or a charge current limit basedat least in part on terminal voltage of the battery. Additionally, basedat least in part on the battery state, the battery control system 14 mayinstruct the battery system 12 to perform one or more control actionsand/or operate in different manners. For example, the battery controlsystem 14 may instruct a switching device to switch from a closed (e.g.,connected) position to an open (e.g., disconnected position) whendischarge current flowing through the switching device exceeds adischarge current limit stored in memory 30.

Additionally, in some embodiments, the battery control system 14 may usethe battery model 42 to predict operation of the battery and/or thebattery system 12. In other words, battery models 42 may model behaviorof the battery system 12, behavior of one or more battery cells 32,and/or behavior of one or more the battery modules 16. Accordingly, insome embodiments, the memory 30 may store one or more different batterymodels 42, for example, to model operation at different levels ofabstraction and/or to model operation of batteries utilizing differentbattery chemistries. In any case, to facilitate providing real-timecontrol, a battery model 42 may generally be computationally facilewhile having a high degree of predictive accuracy.

Generally, the battery control system 14 may use the battery model 42 topredict operational parameters of the battery in addition or as analternative to operational parameters measured by the sensors 34. Inparticular, the battery control system 14 may input one or moreoperational parameter to the battery model 42 and, based at least inpart on operational parameter interrelationships, the battery model 42may output one or more predicted operational parameters. For example,the battery control system 14 may determine terminal voltage of abattery from a sensor 34 and, using the terminal voltage in the batterymodel 42, the battery control system 14 may determine open-circuitvoltage 60 of the battery. In this manner, the battery control system 14may utilize the battery model 42 to determine (e.g., predict) behaviorof the battery, which at least in some instances may facilitate reducingimplementation associated cost of the battery system 12, for example, byenabling number of sensors 34 to be reduced.

An example of a battery model 42, which may be used by a battery controlsystem 14 to model operation of a battery, is shown in FIG. 3. Asdepicted, the battery model 42 utilizes an RC equivalent circuit model.In this way, the battery model 42 may represent one or more ofindividual battery cells 32 and/or one or more of battery modules 16.The battery model 42 relates the model parameters (e.g., a resistance56, a resistance 58, and a capacitance 62) to the operational parameters(e.g., terminal voltage 54, terminal current, and battery temperature)measured by one or more sensor 34. Additionally, the battery model 42may provide a mechanism to estimate the parameters of the battery model42 (e.g., open-circuit voltage 60) in real-time during operation of theautomotive vehicle 10.

In the battery model 42, the resistance 58 (e.g., R₀) may represent anohmic resistance of a current path of the battery module 16, theresistance 56 (e.g., R₁) may represent a charge transfer resistance ofthe battery module 16, and the capacitance 62 (e.g., C₁) may represent adouble layer capacitance of the battery module 16. In the battery model42, the resistances 56 and 58 and the capacitance 62 may generally timeinvariant parameters of the battery module 16. Additionally, theopen-circuit voltage 60, used to determine the state of the batterymodule 16, may generally be a time variant parameter. That is, as thebattery module 16 is charged and discharged over a time, theopen-circuit voltage 60 may increase and decrease over the time. In thisway, the accuracy of the battery model 42, and subsequently theopen-circuit voltage 60 parameter, may increase through validation ofthe model parameters due to the dependence of the value of theparameters upon the model parameters. In any case, as described above, abattery control system 14 may facilitate controlling operation of acorresponding battery system 12 based at least in part on the batterymodel 42 and/or one or more control applications 44.

To help illustrate, an example of a process 70 for controlling operationof a battery system 12 is shown in FIG. 4. Generally, the process 70includes determining operational parameters of a battery (process block72), determining state of the battery based on the operationalparameters (process block 74), and controlling charging and/ordischarging of the battery based on the battery state (process block76). In some embodiments, the process 70 may be implemented at least inpart by executing instructions stored in a tangible, non-transitory,computer-readable medium, such the memory 30, using processingcircuitry, such as the processor 28.

Thus, in some embodiments, the battery control system 14 may determinethe operational parameters of the battery (process block 72). An exampleof a process 86 for determining operational parameters of a battery isdescribed in FIG. 5. Generally, the process 86 includes determiningcurrent flow through a battery (process block 88), determining terminalvoltage of the battery (process block 90), and determining temperatureof the battery (process block 92). In some embodiments, the process 86may be implemented at least in part by executing instructions stored ina tangible, non-transitory, computer-readable medium, such the memory30, using processing circuitry, such as the processor 28.

Thus, in some embodiments, a battery control system 14 may determineoperational parameters of a battery based at least in part on sensordata (e.g., signals) received from one or more sensors 34. For example,the battery control system 14 may determine terminal voltage 54 of thebattery based at least in part on sensor data received from a first(e.g., voltage) sensor 34 (process block 88). Additionally, the batterycontrol system 14 may determine current flow through the battery basedat least in part on sensor data received from a second (e.g., current)sensor 34 (process block 90). Furthermore, the battery control system 14may determine temperature of the battery based at least in part onsensor data received from a third (e.g., temperature) sensor 34 (processblock 92).

In this manner, the battery control system 14 may determine operationalparameters including terminal voltage, current, and/or temperature of abattery. As described above, different battery models 42 may be utilizedto model operation of different batteries. At least in some instances,the operational parameters utilized in different battery models 42 mayvary. For example, one battery model 42 may utilize a first set ofoperational parameters while a different battery model 42 may utilize asecond set of operational parameters.

Thus, in some embodiments, the battery control system 14 may varydetermined operational parameters based at least in part on operationalparameters expected to be utilized in a battery model 42 and/oroperational parameters expected to be utilized in a control application44. For example, when the battery control system 14 uses the batterymodel 42 described in FIG. 3, determination of the terminal voltage andcurrent may be sufficient. However, in some embodiments, the batterycontrol system 14 may nevertheless determine temperature of the batterysince execution of the control application 44 may be dependent onbattery temperature.

Returning to the process 70 of FIG. 4, based at least in part on theoperational parameters of the battery, the battery control system 14 maydetermine state of the battery (process block 74). An example of aprocess 94 for determining one or more battery states is described inFIG. 6. Generally, the process 94 includes determining open-circuitvoltage of a battery (process block 96), determining predicted internalresistance of the battery (process block 98), determining whetherterminal voltage of the battery is greater than a voltage threshold(decision block 100), and determining a charging power limit based onthe predicted internal resistance when the terminal voltage is notgreater than the voltage threshold (process block 102). When theterminal voltage is greater than the voltage threshold, the process 94includes determining real-time internal resistance of the battery(process block 104) and determining the charging power limit based onthe real-time internal resistance of the battery (process block 106). Insome embodiments, the process 94 may be implemented at least in part byexecuting instructions stored in a tangible, non-transitory,computer-readable medium, such the memory 30, using processingcircuitry, such as the processor 28.

Thus, in some embodiments, a battery control system 14 may determine(e.g., predict or estimate) open-circuit voltage 60 of a battery basedat least in part on operational parameters of the battery (process block96). Generally, open-circuit voltage 60 of a battery may vary with itsstate-of charge. Thus, in some embodiments, the battery control system14 may execute a state-of-charge control application 44 to facilitatedetermining the open-circuit voltage 60. For example, by executing thestate-of-charge control application 44, the battery control system 14may determine state-of-charge based at least in part on previous currentflow through the battery (e.g., using a coulomb counting technique).Leveraging their inter-relationship, the battery control system 14 maythen determine open-circuit voltage 60 of the battery based at least inpart on its state-of-charge.

Additionally, the battery control system 14 may determine a predictedinternal resistance of the battery (process block 98). In someembodiments, the battery control system 14 predict internal resistanceexpected to occur based on projected operational conditions(state-of-charge, temperature, power usage, etc.). For example, thebattery control system 14 may determine the predicted internalresistance based at least in part on a predicted driving pattern,current flow through the battery, and terminal voltage 54 of thebattery. In such embodiments, the predicted internal resistance may bedetermined using the following relationship (e.g., model):

$\begin{matrix}{R = \frac{\Delta \; V}{I}} & (1)\end{matrix}$

where R is the predicted internal resistance, ΔV is the differencebetween the present (e.g., real-time) terminal voltage and estimatedopen-circuit voltage, I is the value of the present battery current. Inthis manner, the predicted battery resistance may determine thepredicted battery internal resistance of the battery with appropriateconsideration of charging and/or discharging over a time.

When terminal voltage 54 of the battery is greater than a voltagethreshold, the battery control system 14 may determine a real-timeinternal resistance of the battery (process block 104). In someembodiments, the voltage threshold may be predetermined and stored in atangible, non-transitory, computer-readable medium, such as memory 30.Thus, in such embodiments, battery control system 14 may retrieve thevoltage threshold from the tangible, non-transitory medium forcomparison with the terminal voltage 54.

Additionally, as described above, lifespan of a battery may be reducedwhen its terminal voltage is increased above an upper voltage threshold.To reduce likelihood of sensor or measurement error resulting in actualterminal voltage exceeding the upper voltage threshold, in someembodiments, a battery may begin to be de-rated before its measuredterminal voltage 54 reaches the upper voltage threshold, for example, bylimiting charging and/or discharging of the battery. For example, thebattery control system 14 may de-rate the battery based at least in parton a comparison between its measured terminal voltage 54 and a lowervoltage threshold.

Thus, when the measured terminal voltage is greater than the lowervoltage threshold, the battery control system 14 may determine real-timeinternal resistance of the battery based at least in part on a batterymodel 42. For example, using the battery model 42 shown in FIG. 4, thebattery control system 14 may determine the real-time internalresistance (e.g., combined resistance of resistance 58, resistance 56,and/or capacitance 62) of the battery based at least in part on itsopen-circuit voltage 60, measured (e.g., present or real-time) terminalvoltage 54, and measured (e.g., present or real-time) battery current.In particular, the real-time internal resistance may be equal todifference between the measured terminal voltage 54 and the open-circuitvoltage 60 divided by the measure battery current.

Based at least in part on the real-time internal resistance or thepredicted internal resistance, the battery control system 14 maydetermine a charging power limit. Generally, varying charging powersupplied to a battery may present varying tradeoffs. For example,increasing charging power may increase electrical energy stored in thebattery, but also increase temperature of the battery, which may resultin a decrease in its lifespan. On the other hand, reducing chargingpower (e.g., de-rating) may facilitate decreasing temperature of thebattery, but may also reduce electrical energy stored in the battery.Thus, to facilitate balancing the various tradeoffs, the battery controlsystem 14 may execute an (e.g., state-of-function) control application44 to determine a charging power limit.

In particular, when the measured terminal voltage 54 is greater than thelower voltage threshold, the battery control system 14 may execute thecontrol application 44 using the real-time internal resistance todetermine the charging power limit for the battery (process block 106).As described above, since internal resistance is generally dynamic(e.g., varies with time), the real-time internal resistance may moreaccurately represent the actual internal resistance at a specificinstance in time, for example, compared to the predicted internalresistance. In other words, at least in some instances, determining thecharging power limit in this manner may facilitate achieving a targetbalance between the various tradeoffs, for example, by reducinglikelihood of rapid terminal voltage oscillations.

On the other hand, when terminal voltage 54 of the battery is notgreater than the lower voltage threshold, the battery control system 14may execute the control application 44 using the predicted internalresistance to determine the charging power limit for the battery(process block 102). As described above, the predicted internalresistance may be predicted over a prediction horizon and, thus, beapplicable for more than one specific instance in time. In fact, while areal-time internal resistance may more accurately represent internalresistance at a specific instance in time, accuracy of the predictedinternal resistance may generally be sufficient to determine chargingpower limits during its prediction horizon. Thus, by utilizing theterminal voltage as in indicator of division between such instances,determining charging power limits in this manner may facilitateimproving processing efficiency of a battery control system 14, forexample, by reducing number of times real-time internal resistance isdetermined.

Returning to the process 70 of FIG. 4, based at least in part on itsstate, the battery control system 14 facilitates controlling chargingand/or discharging of the battery, for example, in coordination with ahigher-level (e.g., vehicle) control system (process block 76). To helpillustrate, an example of a process 108 for controlling charging of abattery is described in FIG. 7. Generally, the process 108 includesdetermining a target charging power (process block 110), determiningwhether the target charging power is less than a charging power limit(decision block 112), supplying electrical power at the target chargingpower when the target charging power is less than the charging powerlimit (process block 114), and supplying electrical power at thecharging power limit when the target charging power is not less than thecharging power limit (process block 116). In some embodiments, theprocess 108 may be implemented at least in part by executinginstructions stored in a tangible, non-transitory, computer-readablemedium, such the memory 30, using processing circuitry, such as theprocessor 28.

Thus, in some embodiments, a control system (e.g., battery controlsystem 14 and vehicle control system 26) may determine a target chargingpower (process block 110). As described above, varying charging powermay affect amount of electrical energy stored in a battery and, thus,subsequent ability of the battery to supply electrical power toelectrical devices. Thus, in some embodiments, the battery controlsystem 14 may determine the target charging power based at least in parton target state-of-charge to be achieved by a charging operation.Additionally or alternatively, the battery control system 14 maydetermine the target charging power based at least in part on theelectrical devices to which the battery is expected to subsequentlysupply electrical power.

Based on a comparison between the target charging power and the chargingpower limit, the control system may instruct an electrical power source(e.g., alternator or generator) to adjust electrical power supplied tothe battery. In particular, when the target charging power is less thanthe charging power limit, the control system may instruct the electricalpower source to supply electrical power to the battery in accordancewith the target charging power. On the other hand, when the targetcharging power is not less than the charging power limit, the controlsystem may instruct the electrical power source to supply electricalpower to the battery in accordance with the charging power limit tofacilitate improving operational reliability of the battery, forexample, by reducing likelihood of the charge operation significantlyaffecting (e.g., shortening) subsequent lifespan of the battery.

Thus, one or more of the disclosed embodiments, alone or on combination,may provide one or more technical effects including improvingperformance of a battery system. In particular, the disclosedembodiments may determine power limit for charging and/or discharging abattery by executing control applications, for example, based onvoltage, current, temperature, state-of-charge, battery cell andoperational parameters. For instance, a battery control system mayestimate power limits that are used when outputting control commands(e.g. switching an electrical generator from closed position to an openposition) by using prediction of battery states based at least in parton operational parameters determined by a battery model. Additionally oralternatively, a the battery control system may determine real-time(e.g., measured or actual) operational parameters of the battery systembased at least in part on sensor data received from one or more sensors.In this manner, the techniques described herein enable improvingaccuracy of online (e.g. real-time or near real-time) battery statedetermination. The technical effects and technical problems in thespecification are exemplary and are not limiting. It should be notedthat the embodiments described in the specification may have othertechnical effects and can solve other technical problems.

The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover all modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

What is claimed is:
 1. An automotive electrical system comprising abattery system, wherein the battery system comprises: a batterycomprising terminals configured to be electrically coupled to a one ormore electrical devices in the automotive electrical system; one or moresensors electrically coupled to the terminals of the battery, whereinthe one or more sensors are configured to determine sensor dataindicative of a measured terminal voltage of the battery; and a batterycontrol system communicatively coupled to the one or more sensors,wherein the battery control system is programmed to: determine apredicted internal resistance of the battery, wherein the predictedinternal resistance is determined based on operational conditionsprojected over a prediction horizon. determine a charging power limitused to control supply of electrical power to the battery based at leastin part on the predicted internal resistance when the measured terminalvoltage of the battery is not greater than a lower voltage threshold;and when the measured terminal voltage of the battery is greater thanthe lower voltage threshold: determine a real-time internal resistanceof the battery based at least in part the measured terminal voltage ofthe battery and a battery model that describes relationship betweenmeasured battery parameters and internal resistance of the battery; anddetermine the charging power limit based at least in part on thereal-time internal resistance to facilitate improving operationalreliability of the battery.
 2. The automotive electrical system of claim1, comprising: an electrical power source electrically coupled to theterminals of the battery; and a vehicle control system communicativelycoupled to the battery control system and the electrical power source,wherein the vehicle control system is programmed to: receive anindication of the charging power limit from the battery control system;and instruct the electrical power source to supply electrical power tothe battery in accordance with the charging power limit.
 3. Theautomotive electrical system of claim 1, wherein the battery controlsystem is programmed to: determine the real-time internal resistancecorresponding with a instance in time during the prediction horizon;control charging of the battery at the instance in time using thecharging power limit determined based at least in part on the predictedinternal resistance when the measured terminal voltage of the battery isnot greater than a lower voltage threshold; and control charging of thebattery at the instances in time using the charging power limitdetermined based at least in part on the real-time internal resistancewhen the measured terminal voltage of the battery is greater than alower voltage threshold.
 4. The automotive electrical system of claim 1,wherein: the battery model comprises an RC circuit configured todescribe the relationship of the internal resistance to the terminalvoltage of the battery, current flow through the battery, and anopen-circuit voltage of the battery; and the internal resistance in theRC circuit comprises: a first resistor electrically coupled in seriesbetween the open-circuit voltage and the terminal voltage of thebattery; and a second resistor and a capacitor electrically coupled inparallel between the open-circuit and the terminal voltage of thebattery.
 5. The automotive electrical system of claim 1, wherein: theone or more sensors are configured to determine sensor data indicativeof a measured current flow through the battery; and to determine thereal-time internal resistance, the battery control system is programmedto: determine open-circuit voltage of the battery; and determine thereal-time internal resistance of the battery based at least in part ondifference between the measured terminal voltage of the battery and theopen-circuit of the battery divided by the measured current flow throughthe battery.
 6. The automotive electrical system of claim 5, wherein, todetermine the open-circuit voltage of the battery, the battery controlsystem is programmed to: determine an initial state-of-charge of thebattery; determine a current state-of-charge of the battery based atleast in part on current flow through the battery between the initialstate-of-charge and the current state-of-charge; and determine theopen-circuit voltage of the battery based at least in part on thecurrent state-of charge of the battery.
 7. The automotive electricalsystem of claim 5, wherein, to determine the open-circuit voltage of thebattery, the battery control system is programmed to: instruct thebattery system to electrically disconnect the battery from the one ormore electrical devices; and determine the open-circuit voltage of thebattery based at least in part on the measured terminal voltage afterthe battery is maintained electrically disconnected from the one or moreelectrical devices a duration greater than a rest duration threshold. 8.The automotive electrical system of claim 1, wherein: the one or moresensors are configured to determine sensor data indicative of measuredcurrent flow through the battery; and to determine the predictedinternal resistance, the battery control system is programmed to:determine a predicted driving pattern, wherein the predicted drivingpattern comprises projected battery states over the prediction horizon;determine a voltage change between the measured terminal voltagerelative to a previous terminal voltage of the battery; and determinethe predicted internal resistance based at least in part on the voltagechange multiplied by the measured current flow through the battery anddivided by the predicted driving pattern.
 9. The automotive electricalsystem of claim 1, comprising a temperature sensor configured todetermine sensor data indicative of temperature of the battery, whereinthe battery control system is programmed to adjust model parameters ofthe battery model based at least in part on the temperature of thebattery.
 10. The automotive electrical system of claim 1, wherein thebattery control system is programmed to instruct the battery system toelectrically disconnect the battery from the one or more electricaldevices when the measured terminal voltage of the battery exceeds anupper voltage threshold greater than the lower voltage threshold tofacilitate improving lifespan of the battery.
 11. The automotiveelectrical system of claim 1, wherein the battery comprises: alithium-ion battery cell electrically coupled between the terminals; ora lithium-ion battery module comprising a plurality of battery cellselectrically coupled between the terminals.
 12. A method for controllingcharging of a battery cell in an automotive vehicle, comprising:determining, using a control system, measured terminal voltage of thebattery cell based at least in part on sensor data received from a firstsensor; determining, using the control system, a predicted internalresistance of the battery cell, wherein the predicted internalresistance comprises based on projected operational conditions projectedover a prediction horizon; determining, using the control system, acharging power limit by: determining the charging power limit based atleast in part on the predicted internal resistance of the battery cellwhen the measured terminal voltage of the battery cell is not greaterthan a lower voltage threshold; and determining the charging power limitbased at least in part on a real-time internal resistance of the batterycell when the measured terminal voltage of the battery cell is greaterthan the lower voltage threshold, wherein the real-time internalresistance of the battery cell is determined based at least in part on abattery model that relates measured operational parameters to modelparameters comprising internal resistance; and instructing, using thecontrol system, an electrical power source to adjust charging powersupplied to the battery cell based at least in part on the chargingpower limit when a target charging power is greater than the chargingpower limit.
 13. The method of claim 12, wherein determining thepredicted internal resistance comprises: determining a predicted drivingpattern of the automotive vehicle, wherein the predicted driving patterncomprises battery states projected over the prediction horizon;determining a voltage change of the measured terminal voltage relativeto a previous terminal voltage of the battery cell; and determining thepredicted internal resistance based at least in part on the voltagechange multiplied by the measured current flow through the lithium-ionbattery module and divided by the predicted driving pattern.
 14. Themethod of claim 12, comprising: determining, using the control system,measured current flow through the battery cell based at least in part onsensor data received from a second sensor; and determining, using thecontrol system, the real-time internal resistance of the battery cellwhen the measured terminal voltage of the battery cell is greater thanthe lower voltage threshold by: determining open-circuit voltage of thebattery cell; and determining the real-time internal resistance of thebattery cell based at least in part on difference between the measuredterminal voltage of the battery cell and the open-circuit voltage of thebattery cell divided by the measured current flow through the batterycell.
 15. The method of claim 14, wherein determining the open-circuitvoltage of the battery cell comprises: determining state-of-charge ofthe battery cell based at least in part on the measured current flowthrough the battery cell; and determining the open-circuit voltage ofthe battery cell based at least in part on the state-of-charge of thebattery cell.
 16. The method of claim 12, comprising instructing, usingthe control system, a switching device electrically coupled between thebattery cell and the electrical power source to switch to an openposition when the measured terminal voltage of the battery cell exceedsan upper voltage threshold greater than the lower voltage threshold. 17.A tangible, non-transitory, computer-readable medium storinginstructions executable by one or more processors of an automotivecontrol system, wherein the instructions comprise instructions to:determine, using the one or more processors, measured terminal voltageof an automotive battery module based at least in part on sensor datareceived from a first sensor; determine, using the one or moreprocessors, a predicted internal resistance of the automotive batterymodule expected to occur over a prediction horizon; determine, using theone or more processors, a charging current limit by: determining thecharging current limit based at least in part on the predicted internalresistance of the automotive battery module when the measured terminalvoltage of the automotive battery module is not greater than a voltagethreshold; and determining the charging current limit based at least inpart on a real-time internal resistance of the automotive battery modulewhen the measured terminal voltage of the automotive battery module isgreater than the voltage threshold, wherein the real-time internalresistance of the automotive battery module is determined based at leastin part on a battery model that relates measured battery parameters tomodel parameters comprising internal resistance; and instruct, using theone or more processors, the automotive battery module to supplyelectrical power to an electrical device in an automotive vehicle basedat least in part on the discharging power limit.
 18. The tangible,non-transitory, computer-readable medium of claim 17, comprisinginstructions to: determine, using the one or more processor, measuredcurrent flow through the automotive battery module based at least inpart on sensor data received from a second sensor; and determine, usingthe one or more processors, the real-time internal resistance of thelithium-ion battery cell when the measured terminal voltage of theautomotive battery module is greater than the voltage threshold by:determining open-circuit voltage of the automotive battery module; anddetermining the real-time internal resistance of the automotive batterymodule based at least in part on difference between the measuredterminal voltage of the battery cell and the open-circuit voltage of thebattery cell divided by the measured current flow through the batterycell.
 19. The tangible, non-transitory, computer-readable medium ofclaim 18, wherein the instructions to determine the open-circuit voltageof the automotive battery module comprise instructions to: determinestate-of-charge of the automotive battery module based at least in parton the measured current flow through the automotive battery module; anddetermine the open-circuit voltage of the automotive battery modulebased at least in part on the state-of-charge of the automotive batterymodule.
 20. The tangible, non-transitory, computer-readable medium ofclaim 17, wherein the instructions to determine the predicted internalresistance comprise instructions to: determine a predicted drivingpattern of the automotive vehicle, wherein the predicted driving patterncomprises battery state projected over the prediction horizon; determinea voltage change of the measured terminal voltage relative to a previousterminal voltage of the automotive battery module; and determine thepredicted internal resistance based at least in part on the voltagechange multiplied by the measured current flow through the automotivebattery module and divided by the predicted driving pattern.